Sarah Shourd, one of three American hikers jailed for more than a year in Iran, returned to the United States on Sunday, saying she was "one-third free" and appealed to Iran to release her fiancé and another American friend.

Shourd's comments, made in New York, came as Iranian President Mahmoud Ahmadinejad proposed an apparent swap, suggesting in an interview on ABC that the United States should engineer the release of eight Iranians incarcerated overseas.

Ahmadinejad, in New York for the U.N. General Assembly, said the Iranian government "took a huge humanitarian measure" in releasing Shourd. As such, he said the United States should return the favor and release "the Iranians who were illegally arrested and detained here in the United States."

Shourd, 32, arrived in the United States before dawn on Sunday on a flight from Oman. The Omani government played a key role in negotiating her release. It flew her out of Tehran on a plane owned by the Omani royal family. It was not clear, however, who paid her $500,000 bail to Iranian authorities.

Shourd's two fellow hikers - her fiancé, Shane Bauer, and Joshua Fattal, both 28 - remain under arrest in Evin Prison near Tehran, and there is no sign that they will be released anytime soon.

"I stand before you today only one-third free," Shourd said Sunday, as she pledged to work tirelessly until Iran releases the two men. "The only thing that enabled me to cross the gulf from prison to freedom alone was the knowledge that Shane and Josh wanted with all their hearts for my suffering to end. My life begins the day I can go and pick them up."

As with her previous statements in Tehran the day she was released and in Oman, Shourd did not criticize Iran for jailing her for more than a year. In fact, she praised the Iranian government and Ahmadinejad for her "compassionate release."

Shourd, Bauer and Fattal were arrested in the summer of 2009 by Iranian border guards after allegedly wandering into Iranian territory. Shourd said Sunday that the trio had gone hiking at an Iraqi waterfall - a well-known local tourist attraction - and that if they had crossed a border it was unmarked.

Subsequently they were all indicted in Iran on charges of espionage. Shourd denied those allegations: "We committed no crime, and we are not spies."

The hikers' case has heightened tensions between the United States and Tehran even as the Obama administration has sought to further pressure Iran to abandon what it suspects is the nation's nuclear weapons program. The Obama administration spearheaded efforts to tighten sanctions on Iran for its refusal to cooperate with international inspections of its uranium enrichment program.

During the ABC interview, Ahmadinejad said his country is "ready to discuss" the nuclear issue. "I think we will have a plan to discuss things," he said on ABC's "This Week." He did not elaborate, but Iran from time to time has announced that it is ready for substantive talks on the issue.

In another interview with ABC, Secretary of State Hillary Clinton said the enhanced sanctions against Iran were "biting."

"The Iranian regime is quite worried about the impact on their banking system, on their economic growth," Clinton said.

Ahmadinejad countered that the sanctions were "pathetic."

Ahmadinejad did not specify which Iranians he wanted to see released. Over the course of the last few years, the United States has either arrested or helped other countries arrest several Iranians on charges related to smuggling restricted weapons-related technology.

Tehran is reportedly trying for find a former deputy defense minister, Ali-reza Asgari, who disappeared in Turkey three years ago. He is believed to have either defected or been kidnapped by intelligence agencies. Another Iranian, Omid Khalili, is being held in federal prison in the United States after pleading guilty to charges of illegally exporting restricted technology - spare parts for Iran's aging American-built air force.

Shourd's mother, Nora, had said that while her daughter had been detained in Iran she had some health issues, including a lump in her breast and precancerous cervical cells. On Sunday, Sarah Shourd said that she had been checked by doctors in Oman and that "I'm physically well."